clear() error for perspective-viewer

[stevenvachon]

Bug Report

Steps to Reproduce:

const viewer = document.querySelector('perspective-viewer');

viewer.clear(); // throws
viewer.update([]);

Expected Result:

No error thrown.

Actual Result:

TypeError: Cannot read property 'clear' of undefined
    at HTMLElement.clear (some-file.js:1)

Probably caused by an inner this.table.clear() (or similar) when the table had not been instantiated.

Environment:

• "@finos/perspective-viewer": "^0.4.0-rc.4"
• Node.js v12.14.1
• macOS 10.15.2

[texodus]

Yes, this is precisely right - clear() requires a an existing table. We should sanitize for these cases in perspective-viewer.